We have a big south facing wall of the house, which I think would likely be great for Solar.

I'm wondering if it's viable to install one panel a year for several years, or if Solar is kind of a "go big or go home" kind of thing?

A few neighbors have solar, mostly on the Roof. (the roof ridge of our house is almost directly north/south, so there is no south facing roof space).
It seems that there is a big initial investment in the "interface" (I don't know the technical word) that connects the Solar panels to the House main and the city utilities.

It's is viable / possible to buy an "interface" that could eventually support 10ish panels, and add in one panel a year? Or does everything have to scaled to the final size from the very beginning and install it all at once?